Driver side airbag module cover and horn switch

Abstract: An airbag cover (10) is provided with a membrane horn switch (18) which is more reliable than prior art switches. A portion of the cover is thinned to provide a flexible horn actuation area (14). The membrane switch is mounted against the inner surface of the horn actuation area and is backed by a rigid panel (20) mounted to the cover.

Description: This invention relates to motor vehicle airbags. More particularly, it relates to a driver is side airbag module cover of the kind defined in the preamble of claim 1, said module cover having an integral horn switch which is easily and reliably actuated. US-A-5 186 490 shows a module cover of the same kind. Typically a driver side airbag module is mounted within a motor vehicle's steering wheel. This is the same area which conventionally includes the horn switch. Accordingly, the resilient thermoplastic airbag module cover has also served to actuate a horn switch. One way in which this has been accomplished has been to mount a membrane type switch on the back or inner surface of the airbag module cover. Membrane type switches conventionally comprise two very thin sheets having conductive coatings which are normally separated by thin spacers. Pressure on the switch presses the conductive surfaces together to close a circuit and actuate the horn. The thickness of such a switch may be only, for example, approximately .25 mm thick. Obviously in order to actuate a membrane switch, the force applied by the driver must be able to compress the switch. In prior art installations, the membrane switch could only be compressed against the folded airbag itself. As a result, a fairly substantial degree of cover depression was required. The result was less than optimum reliability and slowed reaction in emergency situations. The present invention consists in a driver's side air bag module cover having a front outer surface and a rear inner surface which comprises: a relatively flexible horn actuation area defined by a region of said cover and depressible from its front surface by a driver; a membrane type horn switch mounted behind said horn actuation area on the rear surface of said cover; and a substantially rigid back panel mounted to the rear surface of said cover and enclosing said horn switch therebetween, characterized in that said horn actuation area is a thinned area of the rear inner surface, the membrane horn switch being mounted within and substantially filling said thinned area and the rigid back panel overlapping the thinned area. There can thus be provided an improved airbag cover and horn switch assembly having increased reliability and emergency actuation response. A preferred embodiment of the invention will now be described with reference to the accompanying drawings wherein: FIG. 1 is the driver's view of an airbag cover in accordance with this invention; FIG. 2 is an elevational view of a back panel employed in the invention; FIG. 3 is a cross-section taken substantially along the line 3-3 of Fig. 1 showing the elements of the invention in exploded format; FIG. 4 is a view similar to Fig. 3 showing the elements assembled; and FIG. 5 is an enlarged cross-sectional detail of the horn actuation area of the invention. Fig. 1 illustrates a thermoplastic cover 10 for a driver side airbag module. The view of the cover is that of the driver and the cover would be positioned within the automotive steering wheel. The normal thickness of the front wall of the cover 10 is on the order of 2.5-3.0 mm. The rear surface of the cover 10 is provided with conventional mounting lugs 12 (Fig. 3). In accordance with the present invention, a portion of the cover 10 is reduced in thickness to approximately 1.0-2.0 mm to provide a horn actuation area 14. The thinning of this area increases its flexibility. In the illustrated embodiment the horn actuation area 14 is surrounded by thermoplastic posts 16 which extend rearwardly from the inner surface of the cover 10. The dimensions of the horn actuation area 14 are such as to receive therein a membrane type horn switch 18 which substantially fills the horn actuation area 14. A relatively rigid back panel 20 is molded to fit the contour of the inner surface of the cover 10 and is dimensioned to slightly overlap the horn actuation area 14. It is provided with mounting holes 22 which are arranged to receive the posts 16. The back panel 20 may be, for example, polypropylene or filled polypropylene. In one embodiment, it has a thickness of 1.5-2.5 mm. It is mounted by means of the holes 22 onto the posts 16 which are then heat staked as illustrated in Fig. 5 to firmly support the horn switch 18 between the back panel 20 and the horn actuation area 14. In the illustrated embodiment, it will be seen from Fig. 5 that the horn actuation assembly is mounted just below one of the airbag tear seams 24 in the cover 10. Referring now to Fig. 5, it will be clearly seen that the membrane type horn switch 20 is sandwiched between a thin and flexible horn actuation area 14 and a relatively rigid back panel 20. It will also be seen that the back panel 20 overlaps the horn actuation area 14 to provide a stable and rigid pressure surface. Depression of the horn actuation area 14 by the driver will readily compress the horn switch 18 against the back panel 20 without relying on any contact or force applied against the airbag enclosed by the cover. The back panel 20 has been described as secured to the cover 10 by means of heat staking. However, other means of assembly may also be utilised such as thermal bonding or cementing.

Claims: A driver's side air bag module cover (10) having a front outer surface and a rear inner surface which comprises: a relatively flexible horn actuation area (14) defined by a region of said cover and depressible from its front surface by a driver; a membrane type horn switch (18) mounted behind said horn actuation area on the rear surface of said cover; and a substantially rigid back panel (20) mounted to the rear surface of said cover and enclosing said horn switch therebetween, characterized in that said horn actuation area (14) is a thinned area of the rear inner surface, the membrane horn switch being mounted within and substantially filling said thinned area and the rigid back panel overlapping the thinned area. A cover according to claim 1 wherein said cover (10) is made of a thermoplastic material. A cover according to claim 2 wherein said back panel (20) is mounted to said cover (10) by heating the cover. A cover according to claim 3 wherein said back panel is heat staked to said cover.

Inventors: LEONELLI PAUL F, LEONELLI, PAUL F.
Applicants: AUTOLIV ASP INC, AUTOLIV ASP, INC.
Application year: 1994
Main classification: B60R21
IPC codes: B60Q5, B60R21, B62D1, G08B21, B60R16